Vocabulary is defined as the words we must know to communicate effectively. These words can be described as oral vocabulary or reading vocabulary
Scientific research on vocabulary instruction reveals that most vocabulary is learned indirectly, but that some vocabulary must be taught directly. (National Institute for Literacy; NIFL 2001).
The NIFL (2001) also stated that students need to develop effective word-learning strategies that include the following:
For example, if students learn just the four most common prefixes in English
they will have important clues about the meaning of about two thirds of all
English words that have prefixes.
(National Institute for Literacy; (2001). Put reading first: The research building blocks for teaching children to read - kindergarten through grade 3. Jessup, MD: ED Pubs).